Incompatibilties

EconomyShopGui: Shulker quick sell can be used to duplicate items (solution: set sell-shulker-boxes to false in the economyshopgui config.yml)

Any Plugin that removes/adds items or modifies them inside shulkers. Their actions will be overwritten by axshulkers, which can cause items to dupe or allow players to farm money.

Other shulker viewers (for obvious reasons)

Plugins that have a shulker view might get desynced and show the wrong items (note: if you find something like this and know how to replicate it, we can patch it)